Tag: rainbows

Convection and Colors

There is no need for me to say that it has been incredibly hot and humid here in northern Virginia. It’s the same pretty much everywhere in the U.S. right now. So I’m saying it for my non-U.S. readers so that they have the context for the post. Hot. And humid. For some reason, news outlets feel the need to report weather events like these in great detail. It’s something that really needs no reporting since we can all experience it by walking out the front door. But they do it anywhere. Temperature is never good enough. The fact that it is 95°F (35°C for the rest of the world) is just not newsworthy. Instead they use “heat index” which factors in humidity to result in a “feels like” temperature. Yesterday, it “felt like” 110°F (43°C). “Heat index” is the opposite of “wind chill.”

I think both of these are ridiculous measurements. If you take a thermometer outdoors, it registers the temperature. Why do we need to exaggerate it with something that a scientific instrument doesn’t even register?

I digress. One side effect of hot, humid weather is convection. The heat provides energy for the atmosphere and that energy is what generates thunderstorms, which typically popup almost out of nowhere in the evenings. We’ve had several of these this week. Lots of thunder, lightning, and some brief but powerful wind and rain. These tend do happen early in the evening, and once the storm blows over, the sun returns, which sometimes results in something beautiful. Take, for example, the image above, which I captured after our evening walk (after the storms had passed).

Rainbows are much more worthy of a news report (or a blog post) than heat index or wind chill, if you ask me.

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The Bridge of the Gods

Okay, someone really needs to reprint Isaac Asimov’s excellent essay, “The Bridge of the Gods” which is all about light and rainbows. I’ve been seeing stuff all over about remarkable “double-rainbows” as if this is a new or even a rare phenomenon, but as Asimov explains in his essay, there is a very good explanation not only for the formation of a double-rainbow, but the geometry behind it.